The present invention relates generally to the field of vibrating conveyors, and in particular to parts feeders for feeding electronic components to "pick and place" machines which mount such components on, for example, printed circuit boards.
The assembly of surface mounted printed circuit boards required the placement of a wide variety and large number of small electronic components on the surface of the board in precisely located, predetermined positions. The repetitive nature of this task has led to the development of computer controlled, automatic "pick and place" machines which pick up electronic components from a "pick" station, move the component to the printed circuit board, and "place" the component at a precisely defined, predetermined location on the circuit board. To maintain a steady supply of components at the "pick" station, like components are packaged in elongate, open ended tubes. A plurality of tubes, each containing different components, are mounted on a vibrating feed tray such that the components advance out of the tubes. To guide the components to their respective "pick" station, channels or troughs must be provided on the tray. It is critical that each channel be properly dimensioned corresponding to the respective components and tubes so that the component is oriented in a predictable fashion when it arrives at the "pick" station. If not properly oriented, the component may not be able to be lifted from the "pick" station, or if it is lifted, it will not be placed in the proper orientation on the printed circuit board.
Many designs have been utilized for guiding the components through channels or troughs. Typically, an array of such troughs are formed on the feed tray which, in turn, is secured to a vibrator. Early attempts at accommodating a wide array of component parts having varying shapes and sizes was to machine a tray exhibiting a plurality of fixed channels of different sizes. This approach proved effective for the particular application for which the tray was machined, but a change in any of the component parts to be fed necessitated machining a new tray. Further, since the tray was machined for a specific application, it was seldom, if ever reusable, and thus the cost of employing such units proved very expensive.
Accordingly, there is a need for an adjustable feed tray, which would enable one to reuse the tray for feeding a variety of different sized components. One approach in the prior art of providing such adjustability was to provide a tray having fixed channel members, and adding spacers to change the width of the channel. The problem with an arrangement of this type was that the troughs were of a width predefined by the fixed channel members, and could therefore only be narrowed. Thus, if the component to be used was wider than the trough, an entire new tray would have to be machined. Further, due to space limitations on the tray, there is a direct trade off between having wider channels and having a large number of channels. Thus, the greater the distance between fixed channel members, the greater the width of the channel, but the smaller the number of channels available.
Another approach to providing the much needed adjustability of the width of the troughs was to provide a tray having a plurality of movable, vertical side walls, whereby two adjacent side walls form a channel. In this arrangement, when it was desired to adjust the width of the channel to accommodate differing sized parts, the side walls were moved laterally to either widen or narrow the channel. The problem with such lateral movement was that the widening of one channel necessarily narrowed the adjacent channel. Thus, when it was desired to change the width of one channel, adjustment of the adjacent channels was also necessitated. Since the width of each channel must be precisely selected to provide the necessary tolerances with respect to the component being fed through the channel, it is a time consuming task to properly align the side walls so that all of the channels are properly dimensioned.
Accordingly, there is a need in the art for a feed tray which allows flexibility as to different size parts, quick and precise adjustment of the channels or troughs on the tray, and which allows a wide selection of channel widths without necessarily limiting the number of channels available.